A crucial issue in microRNA (miRNA) detection is the lack of sensitive method capable of detecting the low levels of miRNA in RNA samples. Herein, we present a sensitive and specific method for the electrocatalytic detection of miR-107 using gold-loaded nanoporous superparamagnetic iron oxide nanocubes (Au-NPFe₂O₃NC). The target miRNA was directly adsorbed onto the gold surfaces of Au-NPFe₂O₃NC via gold-RNA affinity interaction. The electrocatalytic activity of Au-NPFe₂O₃NC was then used for the reduction of ruthenium hexaammine(III) chloride (RuHex, [Ru(NH₃)₆]³⁺) bound with target miRNA. The catalytic signal was further amplified by using the ferri/ferrocyanide [Fe(CN)₆]^3-/4- system. These multiple signal enhancement steps enable our assay to achieve the detection limit of 100 aM which is several orders of magnitudes better than most of the conventional miRNA sensors. The method was also successfully applied to detect miR-107 from cancer cell lines and a panel of tissue samples derived from patients with oesophageal squamous cell carcinoma with excellent reproducibility (% RSD = < 5%, for n = 3) and high specificity. The analytical accuracy of the method was validated with a standard RT-qPCR method. We believe that our method has the high translational potential for screening miRNAs in clinical samples.

microRNA（miRNA）检测中的关键问题是缺乏能够检测RNA样品中低水平miRNA的灵敏方法。在这里，我们提出了使用载金的纳米多孔超顺磁性氧化铁纳米立方体（Au-NPFe ₂ O ₃ NC）对miR-107进行电催化检测的灵敏而特异的方法。靶标miRNA通过金-RNA亲和力相互作用直接吸附到Au-NPFe ₂ O ₃ NC的金表面上。然后，使用Au-NPFe ₂ O ₃ NC的电催化活性还原氯化六胺六氯化钌（RuHex，[Ru（NH ₃）₆ ] ³⁺）与靶标miRNA结合。通过使用亚铁/亚铁氰化物[Fe（CN）₆ ] ^{3- / 4-}系统进一步放大催化信号。这些多重信号增强步骤使我们的测定能够达到100 aM的检测限，这比大多数常规miRNA传感器要好几个数量级。该方法还成功地用于检测癌细胞系和一组食管鳞状细胞癌患者组织样本中的miR-107，具有良好的重现性（％RSD = <5％，n = 3），且特异性高。该方法的分析准确性已通过标准RT-qPCR方法进行了验证。我们相信我们的方法具有筛选临床样品中miRNA的高翻译潜力。